1. Field of the Invention
The present invention relates to a thermoplastic resin composition excellent in Freon resistance and in mechanical properties, which comprises a diene rubber-containing styrene resin, a vinyl resin-containing acrylic rubber polymer obtained by polymerizing a vinyl monomer in the presence of an acrylic rubber polymer and a polymer of a vinyl monomer having a weight average molecular weight of at least 200,000, a process for producing such a thermoplastic resin composition, and a synthetic resin composite consisting essentially of a shaped product of the thermoplastic resin composition and a urethane foam.
2. Discussion of Background
Diene rubber-containing styrene resins represented by ABS resins have high impact resistance and excellent rigidity, mold-processability, gloss and appearance, and they are widely used for industrial parts and household electrical equipments. ABS resins have environmental stress-crack resistance against Freon 11 which is a blowing agent for a foamed hard urethane to be used for e.g. heat insulation between an outer box and an inner box of a household refrigerator.
Certain Freons such as Freon 11 presently used as blowing agents have been criticized as ozone layer-destroying factors, and termination of their production is planed from the viewpoint of protection of global environment. Under the circumstances, use of substitute Freons which are less likely to destroy the environment, is planed. However, substitute Freons such as Freon 141b (i.e. 1,1-dichloro-1-fluoroethane) and Freon 123 (i.e. 1,1-dichloro-2,2,2-trifluoroethane) which are expected to be used as blowing agents, have high penetration power into resins as compared with Freon 11. Accordingly, if an ABS resin is used for a synthetic resin composite produced by using such a substitute Freon as a blowing agent, cracking is highly likely to result.
Among ABS resins, a so-called high nitrile resin (Japanese Unexamined Patent Publication No. 228860/1987) is available which has a remarkably high acrylonitrile content and which is excellent in Freon resistance. However, a resin having a high acrylonitrile content has drawbacks such that the resin is yellowish and its molded product tends to be yellowish, and it is poor in the heat stability and in the vacuum forming property.